Filter Element and Filter System with a Filter Element

ABSTRACT

A filter element has a filter body with a first end face and a second end face opposite the second end face in a direction of a longitudinal axis of the filter body. A first open end plate is arranged at the first end face. A second closed end plate is arranged at the second end face. The second end plate has a sealing structure and the sealing structure is adapted to seal, when the filter element is installed in a housing, a region between the second end plate and a cover of the housing relative to an interior space of the housing. The sealing structure is a ring surrounding an outside circumference of the second end plate and has a sealing surface directed in radial direction outwardly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German patent application Nos. 102013 014 488.4, filed Sep. 2, 2013; 10 2013 014 489.2, filed Sep. 2,2013; 10 2013 014 507.4, filed Sep. 2, 2013; 10 2013 014 492.2, filedSep. 2, 2013; 10 2013 014 491.4, filed Sep. 2, 2013; and 10 2013 014493.0, filed Sep. 2, 2013. The entire contents of the aforesaid Germanpatent applications being incorporated herein by reference and to thefullest extent of the law.

This application claims the benefit of U.S. provisional patentapplication Nos. 62/038,312, filed: Aug. 17, 2014; 62/038,575, filed:Aug. 18, 2014; 62/038,601, filed: Aug. 18, 2014; 62/038,920, filed: Aug.19, 2014; 62/038,672, filed: Aug. 18, 2014 and 62/038,869, filed Aug.19, 2014. The entire contents of the aforesaid provisional patentapplications being incorporated herein by reference and to the fullestextent of the law.

BACKGROUND OF THE INVENTION

The invention relates to a filter element, in particular for use as anair filter for an internal combustion engine as well as a filter systemfor installation of such a filter element.

DE 29780439 U1 discloses air filter constructions, in which the filterelement and the housing are constructed so that a “precleaning” processtakes place, which already removes coarser dirt from the air before itcomes in contact with the filter element. For example, housings havebeen designed for an air stream deflected therein so that the air streamis first deflected (or circumscribing it) in a circular flow or ahelical pattern around the filter element and larger particles of dirtor suspended particulate matter is deposited based on a cyclone effect.

In conventional systems, a substantial amount of turbulence isassociated with the air stream at the inlet opening into the system.Such turbulence can have an extremely negative effect on the efficiencyof a preliminary separation. In some systems, the housing thereforeencloses an interior structure to prevent this. This can cause prematureclogging of the filter medium with larger suspended particles.Furthermore, the suspended particles may damage the filter element whenthey are carried past the filter medium at a high speed.

DE 29780439 U1 also provides an entire filter array comprising ahousing, a removable and replaceable filter element, essentially asdescribed above, and a precleaning configuration that is constructed andarranged in such a way that the air is guided tangentially when itenters the housing, i.e., in a circular or helical flow pattern, whichflows around the filter element or is guided essentially around thefilter element, at least at the beginning.

One object of the invention is to create a filter element havingimproved flow properties that will permit effective pre-separation ofcoarser particles of dirt.

Another object of the invention is to create a filter system foraccommodating such a replaceable filter element having improved flowproperties, which will permit effective pre-separation of largerparticles of dirt.

SUMMARY OF THE INVENTION

According to one aspect of the invention, the aforementioned objects areachieved with a filter element that has a second end plate with asealing structure so that, when the filter element is installed in ahousing, a region between the second end plate and a cover of thehousing can be sealed with respect to an interior space of the housing.

Favorable designs and advantages of the invention are derived from theadditional claims, the description, and the drawings.

A filter element is proposed comprising a filter body with alongitudinal axis, a first end plate that is open or closed and isarranged on an end face and a second end plate arranged on the opposingend face. The second end plate has a sealing structure so that, when thefilter element is installed in a housing, a region between the secondend plate and a cover of the housing can be sealed with respect to aninterior space of the housing. The first end plate is preferablydesigned to be open, i.e., has a central opening for dischargingfiltered fluid, and the second end plate is designed to be closed.However, the invention is also conceivable with a design having two openend plates or having a single sealing structure or an additional sealingstructure on a first open end plate.

The filter element, whose filter body is designed to be permeable forthe medium to be filtered as intended and which is closed by end platesat both ends with one of the end plates usually being impermeable forthe medium to be filtered, is advantageously arranged in a filter systemin such a way that the medium to be filtered, i.e., dust-laden air, forexample, flows through an inlet into the housing and is passedtangentially by the filter element. Due to the tangential oncoming flowof the filter element, the flow is guided in a rotating motion aroundthe filter element, a so-called cyclone motion. In this cyclonepre-separation, centrifugal forces caused by the rotation of the flowact on any larger particles of dust and dirt that might be present inthe air and it is therefore possible to separate most of these particlesin advance. In the prior art, the medium to be filtered can flow throughthe region between the closed end plate of the filter element and thecover of the housing so that, first of all, turbulence may be created inthe interior space of the housing, which can reduce the efficacy of thecyclone effect. On the other hand, some of the coarser dirt may bedeposited in the region of the end plate. According to the invention,the end plate therefore has a sealing structure which seals the regionbetween the end plate and the cover of the housing from the remaininginterior space of the housing when the filter element is installed.

The sealing structure may be designed as an elastic ring, for example,which is in contact with the exterior circumference of the filter bodydirectly below or at the level of the end plate. If the cover of thehousing is placed on the housing over the filter element, then asuitably designed interior contour of the cover in the form of aninterior cover flange will slide over the sealing structure and willthus seal the space over the sealing structure, i.e., in the region ofthe end plate, with respect to the remaining interior space of thefilter system. This sealing structure in the form of a ring may beconnected by individual webs to the end plate to thereby ensure that,even with a narrow tolerance situation in placement of the cover, thesealing structure cannot be shifted downward and impair the sealingeffect.

To achieve a reliable sealing effect of the sealing structure, it isexpedient when the outside diameter of the sealing structure is designedto be larger than the inside diameter of the interior cover flange,wherein coverage of a few tenths of a millimeter is sufficient,depending on the choice of material. The sealing structure in the formof a sealing lip, for example, is then in close contact with the contourof the interior cover flange. Flow can no longer pass around the regionbetween the end plate and the cover, and the turbulence in the medium tobe filtered is reduced. The degree of preliminary separation achieved bythe filter system is therefore fortunately always increasedsubstantially because the flow can follow the desired cyclone movementbetter and the larger particles of dirt can be deposited on the exteriorwall of the housing and can be discharged through a dirt outlet. Sincethe region between the end plate and the cover is outside of the flowpath, eddies that occur there and deflections of the air flow rotatingin the housing contribute only unnecessarily to the pressure drop of thefilter system. The kinetic energy of the rotating flow at this locationcannot be utilized efficiently for separation of contaminants.

In order to achieve the aforementioned effects and advantages, it may bein particular sufficient when the sealing action of the sealingstructure is dust-proof. A completely flow-proof or waterproof seal istherefore advantageous but is not absolutely necessary technically.

The sealing structure can advantageously enclose a circumference of thesecond end plate in the form of a ring. For example, the sealingstructure may enclose the end plate in the form of an O ring which sitson the radially outside circumference of the end plate. There cantherefore be a very reliable and uniform sealing action of the regionbetween the end plate and the cover of the housing. The fit of thefilter element relative to the inside diameter of the cover may beadjusted in a suitable way by the thickness of the O ring in order toachieve easy assembly of the cover over the housing and/or of the filterelement and also to achieve a reliable seal, on the other hand.

Furthermore, the sealing structure may be interrupted and comprised ofsegments, either regularly or irregularly. Such an arrangement may proveadvantageous when the assembly of the cover turns out to be toodifficult. Assembly can be facilitated by such an interrupted sealingstructure and nevertheless the flow around the region between the endplate and the cover with the medium to be filtered can be suppressed aseffectively as with the continuous arrangement.

In an advantageous embodiment, the sealing structure has a sealingsurface, which is directed radially outward, in particular for sealingon a skirt or a wall section of the cover that is retracted in thedirection of the interior of the housing (displaced inwardly). This hasthe advantage that no permanent axial force that is to be built up bytension on the filter element in the housing is necessary on the sealingstructure during operation, which would additionally increase the axialload on the filter element.

In another advantageous embodiment, the sealing structure is formed by asealing lip running peripherally in a ring shape (annular) around theradial outside circumference of the end plate. The sealing lippreferably extends radially beyond the circumference of the filter bodyand/or the radial outside surface of the end plate.

The sealing structure may advantageously be integrally molded on thesecond end plate. This facilitates assembly of the filter elementbecause the sealing structure cannot be lost during storage or displacedduring assembly in this way. In any case, a sealing structure that fitsthe filter element is also present during assembly and cannot bemisplaced. Due to the fact that the sealing structure can be attached bymolding later on, the material may be selected with a suitableelasticity for the sealing effect and is not limited to the material ofthe end plate.

On the other hand, in another advantageous embodiment, the sealingstructure may also be embodied in one piece (monolithic) with the secondend plate. If the material of the end plate should have an elasticitythat is suitable for the sealing effect, the sealing structure with theend plate may also be integrally molded onto the filter body in oneoperation and thus embodied in one piece (monolithic) with the endplate. This is a very inexpensive way to implement an additional sealingstructure. The advantages mentioned above, namely that the sealingstructure cannot be lost and also cannot be inadvertently switched, alsoapply here.

The first and/or second end plate is/are preferably made of a castingcompound that can be processed in casting molds such as, for example,polyurethane or preferably polyurethane foam. The filter body can thenbe embedded in the end plate material in the casting operation. Theexternal shape of the sealing structure can be predetermined easily bythe casting mold in the radially outer region of the end plate to beformed.

In an advantageous embodiment, the filter body may consist, for example,of filter bellows with zigzag folding (pleating), designed to be closedin the shape of a ring. The pleating can be produced, for example, byknife pleating for longer filter bodies or rotary pleating. The filterbellows may be made, for example, of paper or cellulose or of a fiberblend of synthetic fiber and cellulose. The filter bellows may also beembodied with a smooth surface, rolled and/or with a surface shaped withvarious embossed shapes for reinforcement and/or to create cavities fordeposition of dust. The filter bellows may have a coating and/orimpregnation to repel moisture. Alternatively, it may also be coatedwith nanofibers. The filter body may furthermore be reinforcedstructurally with a fiber wrapping. The use of these materials as thefilter medium constitutes a very economical option for implementing sucha filter element. At the same time, the shaping described here offers astable configuration so that a self-supporting design of the filter bodyand thus favorable assembly properties are provided.

The filter element may expediently be used as an air filter, inparticular as an air filter for an internal combustion engine. Thereliable operation of internal combustion engines is also based onreliable and favorable filtering of the intake air for the combustionoperation. The filter element described here represents an economicalpossibility for doing so.

Use of the filter element as a particle filter, in particular as aparticle filter for an internal combustion engine is also advantageous.Here again, reliable assembly and economical replaceability of thefilter element described here are of crucial importance.

According to another aspect, the invention relates to a filter systemhaving an inventive filter element comprising a housing which isconstructed essentially to be concentric about a longitudinal axis, acover that seals the housing and is also constructed to be concentricabout the longitudinal axis, an inlet arranged on the housing and/orcover for supplying the medium to be filtered, in particular air,wherein an outlet for discharging the filtered medium is provided on thehousing so that it is concentric with the longitudinal axis, a skirt ora wall section that is retracted (displaced inwardly) in the directionof the interior of the housing on the cover or on the housing with whichthe sealing structure of the filter element is in contact so that thevolume region formed axially between the end plate and the cover or thehousing is separated from the flow-through region of the housing whichsurrounds the filter body in a ring shape.

Thus a sealing contour which corresponds to a radial seal on the firstend plate of the filter element is provided on the housing in the regionof the outlet, so that the filter element is arranged interchangeably inthe housing of the filter system. The important advantage of such afilter system lies in the secure and stable assembly of the filterelement as well as a very economical interchangeability of the filterelement in a service situation. Rapid replaceability is extremelyimportant especially for short service lives as in the case of use inagricultural and construction machinery.

A cyclone separator may advantageously be provided in the region of theinlet of the filter system and a dirt outlet may be provided on thehousing or on the cover. This cyclone separator comprises a guidinggeometry, which induces rotation of the medium to be filtered. An inletis preferably directed tangentially into the interior of the housing,preferably at the outlet end of the housing so that the flow is forcedinto a rotational movement around the filter element. Due to thisrotation, the dirt is concentrated in the region of the housing wall andis discharged through a dirt outlet at a suitable location, for example,on the housing cover on the end of the housing opposite the outlet end.Due to the pre-separation of most of the dirt out of the air to befiltered, the service life of the actual filter element can be prolongedsignificantly.

The sealing structure preferably forms a seal with respect to aso-called skirt radially. The skirt is defined as a cylindrical tubularwall, which extends axially from the cover of the housing (or from theother housing part in the region of the outlet) over a portion of thelength of the filter element (for example, between 20% and 40% of thelength of the filter element) into the housing interior and preferablysurrounds the filter element coaxially. Between the skirt and theoutside wall of the housing and/or of the cover, an annular flow regionis thus formed in which the fluid can rotate freely. The skirt surroundsthe filter element at a slight distance, preferably less than 10 mm,especially preferably less than 5 mm. The sealing structure ispreferably in contact with the skirt radially, in particular forming aseal, It has surprisingly been found that the seal thereby obtained forthe region situated between the end plate and the cover and thus theseparation of the region from the flow-through region of the housingresults in an improvement in the cyclone pre-separation performance.

In comparison with a filter system without a skirt extending along thefilter body, in which there is also rotation of the flow in a regionsituated between the end plate and the cover, there is also a positiveeffect due to the seal according to the invention when the skirt or awall section of the cover, which is retracted in the direction of theinterior of the housing or a wall section of the other housing part,extends up to the end plate of the filter element, so that the sealingstructure is in contact with the skirt.

According to another embodiment of the invention, a secondary elementmay be arranged in the interior of the filter element. The secondaryelement, which may consist of a load-bearing structure of a cylindricalconfiguration, which is lined with a permeable filter medium, forexample, a nonwoven, has the function of keeping the outlet of thefilter system closed when replacing the filter element so that no dirtcan penetrate into this region while the filter element is being cleanedor replaced. The secondary element, which may be arranged in theinterior of the filter element concentrically with the longitudinal axisof the filter system, is connected to the housing by means of a screwconnection, for example, and is provided with a seal with respect to thehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages are derived from the following description of thedrawings. The drawings illustrate exemplary embodiments of theinvention. The drawings, the description and the claims contain numerousfeatures in combination. Those skilled in the art will expediently alsoconsider the features individually and combine them into appropriateadditional combinations.

FIG. 1 is a perspective view of a filter system according to oneexemplary embodiment of the invention with a tangential inlet, a centraloutlet, and a dirt outlet at the bottom.

FIG. 2 is a longitudinal section through a filter system according toone exemplary embodiment of the invention.

FIG. 3 shows a filter element with a sealing structure according to oneexemplary embodiment of the invention, integrally molded on the secondend plate.

FIG. 4 is a section through the cover part of a filter system accordingto one exemplary embodiment of the invention, having a sealing structureintegrally molded on the second end plate.

In the Figures, same or similar components are labeled with the samereference numerals. The Figures merely show examples and are not to beunderstood as limiting.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a filter system 100 according to oneexemplary embodiment of the invention, which may be used, for example,as an air filter for an internal combustion engine, having a tangentialinlet 102, a central outlet 104 on one end of the housing, and a dirtoutlet 106 on the bottom. This shows a round filter structure, whichconsists of a housing 108 that is sealed with a cover 110, for example,with a screw closure or a bayonet closure. In use as an air filtersystem, dust-laden air flows into the inlet 102 that is arrangedtangentially to the air filter element installed in the interior so thata rotational movement is induced in the air in the interior of thehousing 108 by a flow guard on the filter element. The filter elementand the oncoming flow guard are not shown in the drawing. Centrifugalforces act on the dust particles in the flowing air due to the cycloneeffect induced by rotational movement of the air so that the dustparticles are partially separated on the housing wall and can flow outof the filter system 100 through the dirt outlet 106. The filter elementis therefore under reduced load and the service life of the filterelement is increased. The cleaned air can be discharged out of thehousing 108 through the central outlet 104.

FIG. 2 shows a longitudinal section through a filter system 100according to one exemplary embodiment of the invention with a tangentialinlet 102, a central outlet 104, and a dirt outlet 106 at the bottom.The housing 108 of the filter system 100 is closed with a cover 110 onone front face 120. A filter element 10 consists essentially of a filterbody 12 which is concentric around the longitudinal axis L and is sealedat the two opposing end faces 15, 17 with a first open end plate 16 anda second end plate 18 which may be made of polyurethane foam or anelastomer. The filter body 12 may consist of filter bellows folded in azigzag pattern (pleated) and closed to form a ring. The pleating may beproduced, for example, by knife pleating for longer filter bodies 12 orby rotational pleating. The filter bellows may be made of paper,cellulose or of a fiber blend of synthetic fiber and cellulose, forexample, and may be finished with a smooth surface, with a surfacedesigned to be rolled and/or embossed in various forms for reinforcementand/or creation of cavities for dust deposition. The filter bellows mayhave a coating and/or impregnation to repel moisture. Alternatively itmay also be coated with nanofibers. The filter body 12 may also bereinforced structurally with a filament winding.

The second end plate 18 has supporting nubs 20 which are preferablyarranged at a regular distance relative to each other in a circulararrangement around the longitudinal axis L and extend axially away fromthe axial outer surface of the second end plate; when installed in thereceiving housing 108, the nubs 20 are supported axially on the cover110 on an inner surface, for example, on an inner contour 114 of thecover 110. A support pipe 14, which is permanently mounted on thehousing, is arranged concentrically around the longitudinal axis L inthe interior 50 of the filter element 10 and is permanently connected tothe housing 108 at the outlet end of the support pipe 14. The surface ofthe second end plate 18 facing the support pipe 14 rests on the open endof the support pipe 14, which faces the end plate 18. When the innercover contour 114 of the cover 110 is pressed onto the end plate 18,this force is transferred through the supporting nubs 20 into the endplate 18 which remains supported on the support pipe 14. The filterelement 10 is stressed axially against the cover 110 in this way andthus against the housing 108 by means of the second end plate 18 andthereby experiences a secure support on the end face 17, i.e., the endof the filter element 10 facing the cover. Since the supporting nubs 20keep the end plate 18 spaced apart from the cover 110, an open region119 is formed between the cover 110 and the end plate 18; this region119 is not filled with material and is also known as dead volume.

In addition, rib-shaped elevations 112 are provided in the interiorcontour 114 of the cover, with which the elastic material of the secondend plate 18 can interlock or in which it can be anchored so that thefilter element 10 is thereby secured against possible turning caused byvibrations during operation. In addition, recesses 22, which permitadditional interlocking or anchoring of the support pipe 14 with the endplate 18, are also conceivable on the end of the support pipe 14 facingthe end plate 18 to thereby ensure a further anti-rotation lockingaction of the filter element 10 to protect from vibration-causedturning.

A radial seal 26, which corresponds to the sealing contour 116 of thehousing 108, i.e., is in sealing contact therewith, is provided on theopposing end face 15 of the filter element 10 on the first end plate 16.The filter element 10 can seal the filtered air space from theunfiltered air space by means of this sealing contour.

Dust-laden air can flow in the direction of the arrow 40 through theinlet 102, which in this case is depicted as a tangential inlet andfacilitates cyclone operation due to the rotational motion of the aircreated by means of a cyclone separator 36. Due to the rotationalmovement, dust particles may be deposited on the interior housing walland discharged out of the filter system 100 due to the force of gravitythrough the dirt outlet 106 when the filter housing 108 is installedhorizontally. This pre-separation takes place in an interior space 118of the housing, preferably on the inside wall of the housing 108 inwhich the dust-laden air can flow freely. Region 119 is arranged betweenthe second end plate 18 and the cover 110 of the housing 108 and canalso be referred to as a dead volume. The region 119 is sealed by asealing structure 24 which is formed in one piece (monolithic) with thesecond end plate 18 and made of the same material so that there cannotbe any circulating flow in the region 119. This sealing structure 24 maybe applied in the form of a ring, for example, on the circumference ofthe end plate 18.

On the other hand, in order to suppress the circulating flow in theregion 119, it is not absolutely necessary for the sealing structure 24to be sealed continuously with the housing 108 and/or cover 110 over thecircumference of the end plate 18. The sealing structure 24 may also beinterrupted and comprised of segments in order to suppress thecirculating flow. As shown in FIG. 2, the sealing structure preferablyforms a radial seal with respect to a so-called skirt 240. The skirt 240is a cylindrical tubular wall which extends axially from the cover 110of the housing 108 (or also from the other housing part 108 in theregion of the outlet 104) over a portion of the length of the filterelement 10 (for example, between 20% and 40% of the length of the filterelement 10) into the housing interior and thereby surrounds the filterelement 10, preferably coaxially. Thus, an annular flow region is formedbetween the skirt 240 and the exterior wall of the housing 108 and/or ofthe cover 110 so that the fluid can rotate freely in this annularregion. The skirt 240 surrounds the filter element 10 at a slightdistance, preferably less than 10 mm, especially preferably less than 5mm. The sealing structure 24 is preferably in sealing contact radiallywith the skirt 240. It has surprisingly been found that the resultingseal of the region 119 situated between the end plate 18 and the cover110 and thus the separation of the region 119 from the flow-throughregion of the housing 108 leads to an improvement in the cyclonepre-separation efficiency.

After partial separation of the dust particles during operation, the airthen flows further through the filter body 12 in the direction of thearrows 42, 44 into the interior 50 of the filter element. Dust particlesabove a certain size, depending on the filter medium, still remaincaught in the filter medium. Depending on the dust input, the filterelement 10 must therefore be replaced after a certain service life. Thefiltered air flows out through the outlet 104 in the direction of thearrow 46.

A secondary element 28 is mounted in the interior 50 of the filterelement 10. This secondary element consists essentially of aload-bearing structure, i.e., the body 52, and a relatively permeablefilter medium, for example, a nonwoven. When the filter element 10 inthe housing 108 is replaced, the secondary element 28 remains behind toprotect the downstream air passage, for example, of an internalcombustion engine, from dust particles and other objects penetratinginto it. The secondary element 28 is inserted at the open end 54 into ahousing seat 58 on the outlet part of the housing 108. The second endplate 18 of the filter element 10 sits on the closed end 55 of thesecondary element 28 so that, when the housing cover 110 is closed, aforce can be directed through the supporting nubs 20 on the end plate 18into the closed end of the secondary element 28 and the secondaryelement 28 is thereby tightly pressed into its housing seat 58. Theclosed end of the secondary element 28 is designed as a handle 56 withwhich the element 28 can be removed again from the housing seat 58 andthus from the housing 108.

Filter systems such as those illustrated in FIGS. 1 and 2 are usuallyused in construction machines and in the field of agricultural machines.They are characterized by a great robustness and have a short servicelife because of the high filtration load. A filter system with a loadedfilter element must tolerate an increase in weight of 10 kg or more.

FIG. 3 shows a view of the filter element 10 according to FIG. 2 with asealing structure 24 designed in one piece (monolithic) with and made ofthe same material as the second end plate 18 according to one exemplaryembodiment of the invention. The filter element 10 consists of a filterbody 12 which is sealed with the end plates 16, 18 at the two end faces15, 17. The second end plate 18 has supporting nubs 20 on the top sidefor axial bracing and radial support in a housing when the filterelement 10 is inserted and the housing is sealed from the outside with acover where the filter element 10 can interlock and be tensioned bymeans of the supporting nubs 20 on the end plate 18. The sealingstructure 24 is represented in FIG. 3 as a radial sealing ring which isdesigned in one piece (monolithic) with the end plate 18 and is made ofthe same material. However, the sealing structure 24 may also beintegrally molded with the end plate 18 by an injection molding process,for example, in a two-component injection molding process, in which thesealing structure 24 is integrally molded as a soft component around ahard, injection-molded end plate 18. In addition, the sealing structure24 could also be implemented as an interrupted structure because acomplete seal is not required for suppressing the circulating flow onthe end plate 18 in the region between the end plate 18 and the cover110 of the housing.

FIG. 4 shows a section through the cover part of a filter system 100according to one exemplary embodiment of the invention, in particularthrough the filter system shown in FIG. 1 with a filter element as shownin FIGS. 2 and 3, wherein a sealing structure 24 that is designed in onepiece and is made of the same material as the second end plate 18 isshown. Illustrated is a portion of the filter element 10 consisting ofthe filter body 12 and the second end plate 18 as well as, in theinterior of the filter element 10, the support pipe 14 mounted in thehousing and also a secondary element 28 mounted also in a housing seat.After mounting the filter element 10 in the housing 108 and closing thecover 110 on the front face 120, the cover 110 presses on the second endplate 18 via the supporting nubs 20. On the other side, the end plate 18presses on the end of the support pipe 14 that is facing the end plate18 and also presses on the closed end 55 of the secondary element 28provided with the handle 56. The drawing shows the cover 110, thesupport pipe 14, and the secondary element 28 penetrating into the endplate 18. Since the material of the end plate 18 is expedientlypolyurethane foam or a similar elastic material, the end plate 18 isactually compressed between the cover 110, support pipe 14, andsecondary element 28 and thereby transmits the force from the cover 110to the support pipe 14 and the secondary element 28. The filter element10 is securely clamped via the end plate 18 in this way and is thus heldsecurely. Furthermore, the end plate 18 also presses the secondaryelement 28 securely into its housing seat.

The sealing structure 24 mounted on the end plate 18 can be seen betweenthe end plate 18 and the cover 110. The sealing structure 24 isresponsible for sealing the interior space of the housing against theregion 119 between the end plate 18 and the cover 110 to thereby preventa circulating flow of unfiltered medium around the region 119.Therefore, soiling of the region 119 is prevented, on the one hand.Furthermore, an increased preliminary deposition of dirt particles isachieved by means of the cyclone effect due to a substantiallyhomogenized flow of the unfiltered medium in the interior space of thehousing.

The sealing structure 24 may be embodied, for example, as an elasticring, which rests on the exterior circumference of the filter body 12directly beneath or at the level of the end plate 18. When the cover 110of the housing 108 is placed onto the housing 108 over the filterelement 10, a suitably designed interior contour of the cover 110, forexample, in the form of an interior cover flange, slides over thesealing structure 24 and therefore seals the space above the sealingstructure 24, i.e., in the region of the end plate 18, with respect tothe remaining interior 50 of the filter system 100. This sealingstructure 24 in the form of a ring may be connected to the end plate 18by means of individual webs to thereby ensure that even with a verytight tolerance situation, the sealing structure 24 cannot be displaceddownward when placing the cover 110 in position and cannot cancel orimpair the sealing effect. The detail view of FIG. 4 shows clearly thatthe sealing structure 24, as shown, is preferably designed in one piece(monolithic) with the end plate 18 which is closed and preferably castof a polyurethane or polyurethane foam.

The sealing structure in this case is formed by a sealing lip thatextends in an annular shape around the radial outside circumference ofthe end plate 18. Its axial extension amounts to only a fraction of thethickness of the end plate 18 in the axial direction. The axialextension of the sealing lip, referred to below as the width, preferablyamounts to less than 10 mm, especially preferably less than 5 mm. Thesealing lip preferably extends radially beyond the circumference of thefilter body 12 and/or the radial outside surface of the end plate 18;the radial extension is preferably between 1 mm and 10 mm.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the inventive principles, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles.

What is claimed is:
 1. A filter element comprising: a filter bodycomprising a first end face and a second end face opposite the secondend face in a direction of a longitudinal axis of the filter body; afirst open end plate arranged at the first end face; a second closed endplate arranged at the second end face; wherein the second end platecomprises a sealing structure and the sealing structure, when the filterelement is installed in a housing, is adapted to seal a region betweenthe second end plate and a cover of the housing relative to an interiorspace of the housing.
 2. The filter element according to claim 1,wherein the sealing structure is a ring surrounding an outsidecircumference of the second end plate.
 3. The filter element accordingto claim 1, wherein the sealing structure has a sealing surface directedin radial direction outwardly.
 4. The filter element according to claim3, wherein the sealing structure is a sealing lip in the form of a ringsurrounding a radial outside circumference of the second end plate. 5.The filter element according to claim 4, wherein the sealing lip extendsradially beyond a circumference of the filter body.
 6. The filterelement according to claim 4, wherein the sealing lip extends radiallybeyond a radial outside surface of the second end plate.
 7. The filterelement according to claim 4, wherein the sealing lip extends radiallybeyond a circumference of the filter body and beyond a radial outsidesurface of the second end plate.
 8. The filter element according toclaim 1, wherein the sealing structure is interrupted and comprised ofsegments.
 9. The filter element according to claim 1, wherein thesealing structure is integrally molded on the second end plate.
 10. Thefilter element according to claim 1, wherein the sealing structure andthe second end plate form a monolithic piece.
 11. The filter elementaccording to claim 10, wherein the sealing structure and the second endplate are made of polyurethane or polyurethane foam cast in a castingmold.
 12. The filter element according to claim 1, wherein the filterbody is folded in zigzag pleats and is formed as a closed ring.
 13. Thefilter element according to claim 12, wherein the filter body is made ofpaper; or cellulose; or of a fiber blend of synthetic fiber andcellulose; or is comprised of a cellulose fiber layer and a syntheticfiber layer.
 14. The filter element according to claim 1 as an airfilter.
 15. The filter element according to claim 1 as an air filter foran internal combustion engine.
 16. A filter system comprising: filterelement according to claim 1; a housing comprising a housing wallconfigured to be essentially concentric about a longitudinal axis of thehousing; a cover attached to the housing and sealing the housing, thecover configured to be essentially concentric about the longitudinalaxis of the housing; an inlet arranged on the housing or on the coverand adapted to supply a medium to be filtered to the housing; a skirt ora wall section disposed in a radial direction inwardly relative to thehousing wall and disposed on the cover or on the housing; wherein thesealing structure of the filter element contacts the skirt or the wallsection so that a volume region formed axially between the second endplate of the filter element and the cover or the housing is separatedfrom a flow-through region of the housing which surrounds the filterbody annularly.
 17. The filter system according to claim 16, furthercomprising an outlet arranged on the housing and adapted to dischargethe medium that has been filtered, wherein the outlet is concentric tothe longitudinal axis, wherein the housing has a sealing contour in thevicinity of the outlet, wherein the sealing contour corresponds with aradial seal provided on the first end plate, wherein the filter elementis adapted to be replaceably disposed in the housing.
 18. A method forimproving a pre-separation efficiency of a filter system, the filtersystem comprising a cylindrical housing with a cover and a cylindricalfilter element that is in the form of a ring and comprises two endplates at opposite end faces, wherein inflowing fluid supplied into anannular flow region between a housing wall of the cylindrical housingand the filter element is induced to rotate, the method comprising:arranging, on the cover or on the housing, a skirt or a wall section ina radial direction inwardly relative to the housing wall; providing asealing structure on an end plate of the filter element; separating theannular flow region from a volume region, formed axially between the endplate with the sealing structure and the housing or the cover, bycontacting the skirt or the wall section with the sealing structure.